1. Field of the Invention
The present invention relates to a semiconductor type yaw rate sensor having a beam structure formed from a semiconductor material.
2. Related Art
A conventional semiconductor type yaw rate sensor is disclosed in JP-A-H.8-148698. In this semiconductor type yaw rate sensor, a beam structure is formed from a semiconductor material and is located a predetermined distance above an upper surface of a substrate. The beam structure is forcibly caused to vibrate in a horizontal direction relative to the substrate surface plane. A yaw rate is detected based on vertical displacement of the beam structure relative to the substrate surface plane.
In this semicondutor type yaw rate sensor, to detect vibrating state of the beam structure in the horizontal direction, a movable gate electrode is provided in the beam structure, and source and drain electrodes are formed in the substrate. Due to this arrangement, the vibrating state of the beam structure in the horizontal direction, that is, forced vibration of the beam structure, is detected as a drain current flowing between the source and drain electrodes. The beam structure is caused to vibrate at a constant resonant frequency based on the detected drain current.
In the above-mentioned conventional yaw rate sensor, however, it is necesary not only to provide the movable gate electrode in the beam structure but also to form the source and drain electrodes in the substrate. Therefore, the structure of the yaw rate sensor becomes complicated.